L5 Life's Border: The Plasma Membrane (General Biology)

Cell/plasma membrane

a selectively permeable barrier at the outer boundary of cells, composed of a phospholipid bilayer and other items

Phospholipid molecule

set of one hydrophilic phosphate head and two hydrophobic fatty acid tails, found in every cell and organelle membrane

Cell membrane

2 layers of phospholipids with tails to the inside

Glycocalyx

an outer layer of the plasma membrane composed of short carbohydrate chains attached to membrane proteins (glycoproteins) or membrane lipids (glycolipids) (aid in cell signaling)

Structural support proteins

peripheral proteins on the interior side on animal cells, bound to the interior cytoskeleton of the cell (provide support/stabilization)

Recognition proteins

membrane proteins that present protein fragments or carbohydrates (glycoproteins) for other cells to bind with (immune system cells bind to protein fragments to determine if cell is healthy/infected)

Receptor proteins for communication

membrane proteins that bind with signaling molecules on exterior of cell and initiate a response in the cell interior (insulin, adrenaline, beta-blockers, anti-histamines)

Transport proteins

transmembrane proteins that help polar, charged (ions) and large molecules in and out of the plasma membrane (proteins, polysaccharides, nucleotides)

Diffusion

movement of molecules or ions from a region of greater concentration to a region of lower concentration

Concentration gradient

difference between highest and lowest solute concentration between solutions, more difference = steeper gradient

Dynamic equilibrium

concentrations of the diffusing substance are the same on both sides of a membrane, resulting in no net change of molecules across the membrane, but everything still moving

Brownian movement

random movement of all particles, whether solid, liquid or gas

Kinetic energy

measure of motion of current use

Potential energy

stored energy from bonds

Osmosis

movement of water across a semi-permeable membrane from a region of higher water concentration (lesser solute concentration) to a region of lower water concentration (greater solute concentration)

Aquaporins

protein channels transport water so cells have control

Tonicity

a measure of the concentration of solutes of one solution relative to the concentration of solutes in another solution

Hypertonic

a solution with a higher solute concentration than another adjacent solution

Isotonic

two solutions with the same concentrations of solutes

Hypotonic

a solution with a lesser solute concentration than another adjacent solution

Lysis

destruction of a cell by rupture/popping (animal)

Plasmolysis

shrinkage of plant cell plasma membrane when placed in a hypertonic solution (both)

Turgor pressure

positive water pressure creating a turgid (=firm) cell (plant)

Passive transport

movement of ions of molecules across the plasma membrane without the use of energy

Simple diffusion

movement of ions or molecules directly through the membrane without the use of a protein channel (transport protein)

Facilitated diffusion

movement of ions or molecules across the plasma membrane through a specialized protein channel

Active transport

movement of ions or molecules across the plasma membrane against the concentration gradient with the use of energy (ATP)

Sodium-potassium pump

maintains concentration of gradient of sodium (Na+) and potassium (K+) inside and outside for cell using ATP

Exocytosis

movement of materials out of the cell through the fusion of the plasma membrane and a transport vesicle

Endocytosis

movement of large molecules into the cell by infoldings of plasma membrane